In 2001, after Joan Russow resigned the leadership of the federal Green Party, Bradshaw was appointed interim leader.[2] Bradshaw helped organize the 2003 Green Party Leadership Convention in Ottawa, and was responsible for moving the party's central office to Ottawa from Toronto. In 2003, he was succeeded as party leader by Jim Harris.

Federally, Bradshaw first ran for office in the general election of 2000.[1] Again campaigning in Ottawa Centre, he received 1529 votes for a fifth-place finish. In 2002, while serving as party leader, he contested a by-election in Bonavista—Trinity—Conception, Newfoundland[6] but received only 139 votes. Bradshaw ran in Newfoundland in an effort to foster a genuinely national party: there has been a history of division between the Terra Nova Green Party, which is the Newfoundland & Labrador Green Party Association, and the federal Green Party.

In the 2004 federal election, Bradshaw campaigned in the rural Ottawa Valley riding of Leeds—Grenville, replacing Jerry Heath who unexpectedly declined to run. Despite the last-minute substitution, Bradshaw received 5.5% of the votes cast (2,722), a significant improvement over the Green Party's previous 1.73%.